Power line communication apparatus

ABSTRACT

A communication apparatus performs communication through a power line. The communication apparatus includes an electrical power plug which is capable of connecting to the power line and provides the communication apparatus with a power supply. The communication apparatus also includes a power line communication unit which performs communication through the power line, and a heat radiator which radiates heat generated from the power line communicator, wherein the heat radiator is disposed at a location where is not to overlap the power plug.

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/182,200, filed Jul. 30, 2008, the content of which areexpressly incorporated herein by reference in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to a power line communication apparatuscapable of performing communication employing a power line as atransmission medium.

2. Background Art

Recently, there has been suggested a power line communication systemcapable of transmitting data by superposing a high-frequency signal on apower line carrying electric power such as commercial power. As such atype of a power line communication system, there is known amulti-carrier transmission communication apparatus capable oftransmitting and receiving a multi-carrier communication signal (forexample, see JP-A-2003-218831).

The power line communication apparatus such as a PLC (Power LineCommunication) modem used in the power line communication system can berealized into various types such as an AC adapter type directlyconnected to an outlet of a power line, a single modem type having afunction of a hub, a router, or the like, and an apparatus-integratedtype integrated into a PC (Personal Computer) or the like. Accordingly,if a signal processor of the PLC modem is designed in accordance with atype of respective apparatus, design cost or manufacture cost may beincreased that much.

An analog signal processor of the PLC modem has a problem in that whenthe analog signal processor is apart from a coupler which separates andcouples a high frequency signal for the power line communication fromand with the power line, noise may increase in the analog high frequencysignal (communication signal of the power line), thereby deteriorating acommunication performance. Meanwhile, it is preferable that the analogsignal processor of the PLC modem and a network interface unit such asEthernet (registered trademark) provided in the subsequent step of thePLC modem are apart from each other as much as possible.

For that reason, various units such as a power supply unit, a signalprocessor, and an interface unit are necessary to be arranged inconsideration of various circumstances of the power line communicationapparatus.

SUMMARY

According to an aspect of the invention, there is provided acommunication apparatus which performs communication through a powerline and a transmission medium different from the power line. Thecommunication apparatus includes: a power board which is provided with apower unit connected to the power line; an interface board which isseparately formed from the power board and is provided with an interfacefor performing communication through the transmission medium; and acommunication board which is separately formed from the power board andthe interface board and is provided with a power line communication unitfor performing communication through the power line and a connectionunit electrically connectable to the power board and the interfaceboard.

According to the invention, there is provided a communication apparatuscapable of configuring a communication board provided with a signalprocessor for power line communication which can be used in common evenin various types of an apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The above advantage of the present invention will become more apparentby describing in detail preferred exemplary embodiments thereof withreference to the accompanying drawings, wherein like reference numeralsdesignate like or corresponding parts throughout the several views, andwherein:

FIG. 1 is a perspective view illustrating an arrangement configurationof major elements of a communication apparatus;

FIG. 2 is a perspective view illustrating a configuration of each boardof the communication apparatus;

FIG. 3A is a perspective view illustrating the assembly process of eachunit of the communication apparatus;

FIG. 3B is a perspective view illustrating the assembly of the uppercasing;

FIG. 3C is a perspective view illustrating the assembly of the uppercasing and the lower casing;

FIG. 4 is a block diagram illustrating an example of a circuitconfiguration of the communication apparatus;

FIG. 5 is a perspective view illustrating an arrangement configurationof the major elements of the communication apparatus;

FIG. 6 is a perspective view illustrating an arrangement configurationof the major elements of the communication apparatus;

FIG. 7 is a perspective view illustrating an arrangement configurationof the major elements of the communication apparatus;

FIG. 8 is a perspective view illustrating an arrangement configurationof the major elements of the communication apparatus; and

FIG. 9 is a perspective view illustrating an arrangement configurationof the major elements of the communication apparatus.

DETAILED DESCRIPTION

FIG. 1 shows a configuration example of an AC adapter-typed PLC modemdirectly connected to an outlet of a power line. The configuration ofthe communication apparatus is not limited thereto, but may be modifiedin various forms.

In a PLC modem 10, a power plug 25 is integrally formed on one outersurface of a lower casing 100 so as to protrude therefrom. The PLC modem10 is of an AC adapter-type which is directly connected to an outlet ofthe power line. A power board 101 on which a power unit is formed, acommunication board 102 on which a signal processor for power linecommunication is formed, and an interface board 103 on which a networkinterface unit of an Ethernet (registered trademark) are housed withinthe lower casing 100.

Three boards are arranged in such a manner that the power board 101 andthe interface board 103 are connected through a power connector 104 tobe arranged on one plane and that the communication board 102, which isseparately formed from the power board 101 and the interface board 103,is erected to the power board 101 and the interface board 103 at asubstantially right angle. In addition, the communication board 102 iselectrically connected to the power board 101 and the interface board103 through a first connector (PLC connector) 105 and a second connector(interface connector) 106, respectively.

The communication board 102 is fixed to a board holding frame 107A of aheat radiator 107 formed by curving a plate-shaped member such as ametal plate or the like using a screw or the like, and is connected tothe power board 101 and the interface board 103 through the firstconnector 105 and the second connector 106, respectively. In addition,the heat radiator 107 is attached and fixed to the lower casing 100along with the interface board 103 by a screw or the like in a fixingportion 107B in a state where the heat radiator 107 holds and fixes thecommunication board 102 to be integrally formed with the power board 101and the interface board 103.

In FIG. 2, the heat radiator 107 is omitted and the power board 101, thecommunication board 102, and the interface board 103 are shown forconvenient explanation.

On the power board 101, a plug receiver 111 of a power plug 25, a coiltransformer 16A and coupling capacitors 16B and 16C of the coupler 16,one part of the power connector 104, one part of the first connector105, and the like are mounted as major components. On the interfaceboard 103, the other part of the power connector 104, one part of thesecond connector 106, a network connection unit 112 housing four modularjacks for network connection, and the like are mounted as majorcomponents. On the communication board 102, the other part of the firstconnector 105, the other part of the second connector 106, a circuit IC(not shown), and the like are mounted as major components. At this time,the first connector 105 and the second connector 106 are positioned atboth ends in a longitudinal direction of the communication board 102 tobe apart from each other. The first connector 105 which serves as a PLCconnector includes a connection portion of a transmission path throughwhich a high frequency analog signal (PLC signal) for PLC istransmitted. The second connector 106 which serves as an interfaceconnector includes a connection portion of a transmission path throughwhich a digital signal containing data, which is transmitted to andreceived from another apparatus through a network interface or the like.

As shown in FIG. 3A, the power board 101, the interface board 103, thecommunication board 102, and the heat radiator 107 are integrallyassembled to be connected to each other. At this time, a base end of thepower plug 25 is inserted into the plug receiver 111 of the power board101, and the power board 101, the interface board 103, and the heatradiator 107 are fixed to the lower casing 100 using a screw. Bossformed at predetermined positions of the lower casing 100 engage withboss holes of the power board 101 and the interface board 103, so thatthe boards are positioned on the lower casing 100.

Subsequently, as shown in FIG. 3B, the boards positioned on the lowercasing 100 are covered with an upper casing 110. As shown in FIG. 3C,the lower casing 100 and the upper casing 110 are fixed to each other byscrews. In the PLC modem 10 assembled in this way, the power plug 15 andthe network connection unit 112 are exposed outside. In addition, thepower plug 25 is configured so as to be connected to an outlet of apower line and the network connection unit 112 is configured so as to beconnected to a network cable. Electric power is supplied through thepower line and the PLC signal is received and transmitted, so that thePLC modem 10 enables data communication to be performed by transmittingdata to another apparatus such as a PC through the network cable.

As described above, the PLC modem 10 includes the power board 101, thecommunication board 102, and the interface board 103. As shown in FIG.4, the power board 101 is provided with the power plug 25, the coupler16, an impedance upper 27, an AC/DC converter 24, and switching powersupply 20. The switching power supply 20 supplies various direct-currentvoltages (for example, +1.2 V, +3.3 V, +10.5 V, and +12 V) to thecommunication board 102 or the interface board 103. The switching powersupply 20 includes, for example, a switching transformer and a DC-DCconverter (which are all not shown). The electric power is supplied fromthe power plug 25 to the switching power supply 20 through the impedanceupper 27 and AC/DC converter 24. The coupler 16 separates and couplesthe PLC signal, which is a high frequency signal, from and to the powerline and includes the coil transformer 16A and the coupling capacitors16B and 16C. The coupling capacitors 16B and 16C are connected to thepower plug 25, and the coil transformer 16A is connected to thecommunication board 102.

The communication board 102 is provided with a main IC (IntegratedCircuit) 11, an AFE/IC (Analog Front END/Integrated Circuit) 12, alow-pass filter (LPF) 13, a driver IC 15, and a band-pass filter (BPF)17, a memory 18, and an Ethernet PHY/IC (Physical layer/IntegratedCircuit) 19. An indicator 23 is connected to the main IC 11. The main IC11 functions as a communication control unit in power linecommunication.

The main IC 11 includes a CPU (Central Processing Unit) 11A, a PLC/MAC(Power Line Communication/Media Access Control layer) block 11C, and aPLC/PHY (Power Line Communication/Physical layer) block 11B. A 32-bitRISC (Reduced Instruction Set Computer) processor is mounted in the CPU11A. The PLC/MAC block 11C manages a MAC layer (Media Access Controllayer) of a transmission signal and a reception signal. The PLC/PHYblock 11B manages a PHY layer (Physical layer) of a transmission signaland a reception signal. The AFE/IC 12 includes a DA converter (DAC: D/Aconverter) 12A, an AD converter (ADC: A/D converter) 12D, and variablegain amplifiers (VGA: Variable Gain Amplifier) 12B and 12C. In addition,the CPU 11A controls operations of the PLC/MAC block 11C and the PLC/PHYblock 11B using data stored in the memory 18 and also controls the PLCmodem 10 as a whole.

The interface board 103 is provided with a hub 28, an indicator 29, andthe network connection unit 112 housing four RJ45 type modular jacks22A, 22B, 22C, and 22D. Network cables for making connection to a PC orlike are connected to the modular jacks 22A, 22B, 22C, and 22D.

Communication by means of the PLC modem 10 in FIG. 4 is performed asfollows. That is, data input to the modular jacks 22A, 22B, 22C, and 22Dis transmitted to the main IC 11 through the hub 28 and the EthernetPHY/IC 19, and a digital transmission signal is generated by performinga digital signal process. The generated digital transmission signal isconverted into an analog signal by the DA converter (DAC) 12A of theAFE/IC 12 and superposed on a transmission path as the PLC signalthrough the low-pass filter 13, the driver IC 15, and the coupler 16 tobe output to a power line 1A through the power plug 25 and an outlet 2.

The signal received from the power line 1A is separated as the PLCsignal via the coupler 16, its gain is adjusted by the variable gainamplifier (VGA) 12C of the AFE/IC 12 through the band-pass filter 17,and the signal is converted into a digital signal by the AD converter(ADC) 12D. The converted digital signal is transmitted to the main IC 11and subjected to a digital signal process to be converted into digitaldata. The converted digital data is output from the modular jacks 22A,22B, 22C, and 22D through the Ethernet PHY/IC 19 and the hub 28.

The PLC modem 10 is configured in such a manner that the power board 101is a separate body from the communication board 102, and thus thecommunication board 102 is separately provided to be connected to thepower board 101 through the connector. In this way, the communicationboard 102 provided with the signal processor for power linecommunication can be used in common in various apparatuses. Accordingly,when a power line communication function is provided to variousapparatuses, the communication board 102 can be used in common.Therefore, since it is not necessary to design a separate communicationboard in accordance with the shape of various apparatuses, design costor manufacture cost can be reduced.

The first connector 105 and the second connector 106 are separatelyprovided in the communication board 102. The first connector 105 isapart from the second connector 106. The coupler 16 is disposed in thevicinity of the first connector 105 and the power board 101, and aninput unit (analog signal processor) for the PLC signal formed on thecommunication board 102 can be connected to the coupler 16 through thefirst connector 105 at a location where they are as close as possible.Accordingly, it is possible to shorten the transmission path for ananalog signal. Moreover, the communication board 102 can come closer tothe coupler 16 by configuring the communication board 102 to be erectwith respect to the power board 101. Furthermore, since thecommunication board 102 and the interface board 103 can be connected toeach other through the second connector 106 at a location which is awayfrom the first connector 105, a transmission path for a digital signalcontaining data transmitted to and received from a network connectorsuch as the Ethernet (registered trademark) which is an interface ofanother apparatus can be apart from the analog signal processor or atransmission path for an analog signal. With such a configuration,interference of noise can be reduced, thereby improving a communicationperformance.

The power board 101 and the interface board 103 may be configured as twoseparate boards, and may be also configured as one integrated board likea base board. When the power board 101 and the interface board 103 areconfigured as the one board, the number of components is reduced. Whenthe power board 101 and the interface board 103 are configured as thetwo boards, the interface board 103 can be exchanged with a differentboard having a different shape of the network connection unit 112 or thelike. Accordingly, it is possible to configure the PLC modem to easilycorrespond to the different number of connection ports, various networktypes, and the like.

The heat radiator 107 is formed by curving a plate-shaped member such asa metal plate having high thermal conductivity and electricalconductivity, and holds the communication board 102 so as to be housedand fixed to the casing. With such a configuration, it is possible tomaintain strength while ensuring sufficient heat radiating capacity andheat radiating area. The heat radiator 107 extends so that at least apart thereof face the power board 101 and is provided so as not tooverlap with the power plug 25 and the plug receiver 111.

A support portion 107D formed to be erected from the interface board 103is disposed in the vicinity of an end portion 107C of an extensionportion facing the power board 101 of the heat radiator 107. With such aconfiguration, even though stress is applied to the heat radiator 107toward the power board 101, the end portion 107C is held by the supportportion 107D, so that displacement of the heat radiator 107 toward thepower board 101 is regulated. At this time, a space between the heatradiator 107 and the power plug 25 or the plug receiver 111 issufficiently ensured. As a modified example of the heat radiator 107,the heat radiator 107 may be formed in a substantially reverse U shapewith respect to the power board 101 and the interface board 103 so thatdisplacement of the heat radiator toward the power board is suppressed.By configuring the heat radiator 107 in this manner, it is possible topreventing contact with the power plug 25 and the like while having asufficient heat radiating function.

Hereinafter, other embodiments regarding to arrangement of the powerboard 101, the communication board 102, and the interface board 103 willbe described with reference to FIGS. 5 to 9.

As shown in FIG. 5, the communication board 102 is disposed so that adirection of a normal line of the communication board 102 is differentfrom a direction of a normal line of the power board 101 and a directionof a normal line of the interface board 103. In addition, thecommunication board 102, the power board 101, and the interface board103 are electrically connected to each other. The power board 101 andthe interface board 103 are arranged on one plane. In addition, thepower board 102 is disposed to be erect at a substantially right anglewith respect to the power board 101 and the interface board 103 arrangedon one plane.

It is possible to allow the outer size of the upper casing 110 forhousing the boards to be small by arranging the power board 101 and theinterface board 103 on one plane, thereby downsizing the PLC modem 10.Moreover, it is possible to ensure a sufficient space for mountingelectronic components on the power board 101 and the interface board103, by disposing the power board 102 to be erect at the substantiallyright angle with respect to the power board 101 and the interface board103 arranged on one plane. In particular, such a configuration isappropriate in mounting electronic components since many large-sizedelectronic components (for example, the coil transformer 16A of thecoupler 16 or the coupling capacitors 16B and 16C) can be mounted on thepower board 101.

In FIG. 5, a longitudinal direction of the communication board 102 issubstantially parallel to a transverse direction of the power board 101and a transverse direction of the interface board 103.

The power board 101, the interface board 103, and the communicationboard 102 are electrically connected to each other through a connector108. The connector 108 has functions of the power connector 104, thefirst connector 105, and the second connector 106 described above.

By allowing the connector 108 to have the functions of the powerconnector 104, the first connector 105, and the second connector 106, itis possible to reduce the number of components used in the PLC modem 10,thereby simplifying a manufacture process of the PLC modem 10.

However, the PLC signal is much influenced by noise occurring from adigital signal for an interface, since the connector 108 has thefunctions of the first connector 105 and the second connector 106. Forthat reason, in the connector 108, it is preferable that an insulatingmember (not shown) is disposed around the transmission path fortransmitting the PLC signal.

It is preferable that the coupler 16 (not shown) is disposed in thevicinity of the connector 108. Since a transmission path for the PLCsignal between the coupler 16 and the connector 108 can be shortened bydisposing the coupler 16 in the vicinity of the connector 108, it ispossible to improve a communication performance of the PLC modem 10.

Like the configuration shown in FIG. 5, a configuration of majorcomponents of the PLC modem 10 shown in FIG. 6 is as follows. That is, adirection of a normal line of the communication board 102 is differentfrom a direction of a normal line of the power board 101 and a directionof a normal line of the interface board 103. In addition, thecommunication board 102, the power board 101, and the interface board103 are electrically connected to each other.

The power board 101 and the interface board 103 are arranged on oneplane. In addition, the power board 102 is disposed to be erect at asubstantially right angle with respect to the power board 101 and theinterface board 103 arranged on one plane, and is disposed between thepower board 101 and the interface board 103.

In the configuration example shown in FIG. 6, since the communicationboard 102 is disposed between the power board 101 and the interfaceboard 103, an area where the communication board 102 overlaps with thepower board 101 and the interface board 103 can be made small.Accordingly, such a configuration is appropriate in mounting electroniccomponents since a large area where electronic components are mounted inthe power board 101 and the interface board 103 and the interface board103 can be ensured.

Moreover, like the configuration example shown in FIG. 5, since thepower board 102 is disposed to be erect at the substantially right anglewith respect to the power board 101 and the interface board 103 arrangedon one plane, a large area where electronic components are mounted inthe power board 101 and the interface board 103 can be ensured. Inparticular, such a configuration is appropriate in mounting electroniccomponents since many large-sized electronic components (for example,the coil transformer 16A of the coupler 16 or the coupling capacitors16B and 16C) can be mounted on the power board 101.

In FIG. 6, a longitudinal direction of the communication board 102 issubstantially parallel to a longitudinal direction of the power board101 and a longitudinal direction of the interface board 103.

The first connector 105 is provided on one main surface of thecommunication board 102 and the second connector 106 is provided on theother main surface thereof. The first connector 105 and the secondconnector 106 can be located at any location of the communication board102, but it is preferable that the first connector 105 and the secondconnector 106 is disposed so as to be spaced from each other. Since aninfluence of noise occurring from the digital signal of an interface forreceiving the PLC signal can be reduced by spacing the first connector105 and the second connector 106, it is possible to improve acommunication performance of the PLC modem 10. In case where the firstconnector 105 and the second connector 106 cannot be arranged to beseparated from each other, an insulating member (not shown) may beprovided at any location of the communication board 102.

In FIG. 6, electrical power is supplied from the power board 101 to theinterface board 103 through the first connector 105 and the secondconnector 106.

In addition, it is preferable that the coupler 16 (not shown) isdisposed in the vicinity of the first connector 105. Since atransmission path for the PLC signal between the coupler 16 and thefirst connector 105 can be shortened by disposing the coupler 16 in thevicinity of the first connector 105, it is possible to improve acommunication performance of the PLC modem 10.

In FIG. 7, the communication board 102, the power board 101, and theinterface board 103 are arranged so that a direction of a normal line ofthe communication board 102, a direction of a normal line of the powerboard 101, and a direction of a normal line of the interface board 103are substantially parallel to each other. That is, the communicationboard 102, the power board 101, and the interface board 103 are arrangedon substantially one plane.

Since an outer size (size in the direction of the normal lines of thecommunication board 102, the power board 101, and the interface board103) of the upper casing 110 can be made small by arranging all theboards on substantially one plane, such a configuration is appropriatein allowing the PLC modem 10 to be thin.

Since the electronic components mounted on the boards can be preventedfrom interfering one another by arranging all the boards onsubstantially one plane even in a case of applying a stress to the PLCmodem 10, it is possible to improve durability or safety of the PLCmodem 10.

In the configuration example shown in FIG. 7, since the communicationboard 102 is arranged between the power board 101 and the interfaceboard 103, an area where the communication board 102 overlaps with thepower board 101 and the interface board 103 can be made equal to thearea shown in FIG. 6. Accordingly, since a large area where electroniccomponents are mounted on the power board 101 and the interface board103 can be ensured, such a configuration is appropriate in mounting theelectronic components.

In FIG. 7, a longitudinal direction of the communication board 102 issubstantially parallel to a longitudinal direction of the power board101 and a longitudinal direction of the interface board 103.

The first connector 105 is provided on one long side of thecommunication board 102 and the second connector 106 is provided on theother long side thereof.

The first connector 105 and the second connector 106 can be provided atany location, but it is preferable that the first connector 105 and thesecond connector 106 are provided to be apart from each other. Since thePLC signal and a digital signal for an interface can be separated oneanother by spacing the first connector 105 and the second connector 106from each other, it is possible to reduce a noise influence of thedigital signal on the PLC signal.

In FIG. 7, electric power is also supplied from the power board 101 tothe interface board 103 through the first connector 105 and the secondconnector 106, like the configuration example shown in FIG. 6.

It is preferable that the coupler 16 (not shown) is disposed in thevicinity of the first connector 105. Since a transmission path for thePLC signal between the coupler 16 and the first connector 105 can beshortened by disposing the coupler 16 in the vicinity of the firstconnector 105, it is possible to improve the communication performanceof the PLC modem 10.

In a configuration example shown in FIG. 8, the communication board 102,the power board 101, and the interface board 103 are arranged so that adirection of a normal line of the communication board 102, a directionof a normal line of the power board 101, and a direction of a normalline of the interface board 103 are substantially parallel to eachother, like the configuration example shown in FIG. 7. That is, thecommunication board 102, the power board 101, and the interface board103 are arranged on substantially one plane.

As shown in FIG. 8, a longitudinal direction of the communication board102 is substantially perpendicular to a longitudinal direction of thepower board 101 and a longitudinal direction of the interface board 103.

Since an outer size (size in the direction of the normal lines of thecommunication board 102 and the like) of the upper casing 110 can bemade small by arranging all the boards on substantially one plane, sucha configuration is appropriate in allowing the PLC modem 10 to be thin.

Since the electronic components mounted on the boards can be preventedfrom interfering one another by arranging all the boards onsubstantially one plane even in a case of applying a stress to the PLCmodem 10, it is possible to improve durability or safety of the PLCmodem 10.

The first connector 105 and the second connector 106 are provided on onelong side of the communication board 102.

The first connector 105 and the second connector 106 can be provided atany location of the one long side of the communication board 102, but itis preferable that the first connector 105 is apart from the secondconnector 106. Since the PLC signal and a digital signal for aninterface can be separated one another by spacing the first connector105 and the second connector 106 from each other, it is possible toreduce a noise influence of the digital signal on the PLC signal.

It is preferable that the coupler 16 (not shown) is disposed in thevicinity of the first connector 105. Since a transmission path for thePLC signal between the coupler 16 and the first connector 105 can beshortened by disposing the coupler 16 in the vicinity of the firstconnector 105, it is possible to improve the communication performanceof the PLC modem 10.

Like the configuration example shown in FIG. 5, the communication board102, the power board 101, and the interface board 103 may be connectedto each other through the connector 108.

It is preferable that the coupler 16 (not shown) is disposed in thevicinity of the first connector 105. Since a transmission path for thePLC signal between the coupler 16 and the first connector 105 can beshortened by disposing the coupler 16 in the vicinity of the firstconnector 105, it is possible to improve the communication performanceof the PLC modem 10.

In a configuration example shown in FIG. 9, the communication board 102,the power board 101, and the interface board 103 are arranged so that adirection of a normal line of the communication board 102, a directionof a normal line of the power board 101, and a direction of a normalline of the interface board 103 are substantially parallel to eachother, and the communication board 102 overlaps with the power board 101and the interface board 103.

Since outer size of the upper casing 110 and the lower casing 100 can bemade small by overlapping the communication board 102 with the powerboard 101 and the interface board 103, such a configuration isadvantageous in miniaturization of the PLC modem 10.

The first connector 105 and the second connector 106 can be provided atany location of the edge of the communication board 102, but it ispreferable that the first connector 105 and the second connector 106 areprovided on a short side of the communication board 102 like theconfiguration example shown in FIG. 9. With such a configuration, sincethe first connector 105 can be disposed apart from the second connector106, it is possible to reduce a noise influence of a digital signal foran interface on the PLC signal.

Electric power is supplied from the power board 101 to the interfaceboard 103 through the first connector 105 and the second connector 106.

Since description regarding to components mounted on the power board101, the communication board 102, and the interface board 103 in FIGS. 5to 9 is the same as that in FIGS. 1 to 4, the repetitive description isomitted.

It is preferable that the coupler 16 (not shown) is disposed in thevicinity of the first connector 105. Since a transmission path for thePLC signal between the coupler 16 and the first connector 105 can beshortened by disposing the coupler 16 in the vicinity of the firstconnector 105, it is possible to improve the communication performanceof the PLC modem 10.

Specifically, the vicinity of the first connector 105 refers to a rangeof a 2 cm radius from the first connector 105 in the description of thecoupler 16.

In this way, the communication board 102 can be configured so as to beused in common in other apparatuses. With such a configuration, it ispossible to improve the communication performance by shortening thetransmission path of an analog signal, since the analog signal processorof the communication board 102 can be disposed in the vicinity of thecoupler 16. Moreover, it is possible to improve the communicationperformance by reducing the noise interference, since the analog signalprocessor provided on the communication board 102 and the networkinterface unit provided on the interface board 103 can be separated fromeach other. Furthermore, it is possible to prevent the heat radiator 107from coming in contact with the input unit of the power line such as thepower plug 25 and the plug receiver 111 while ensuring a sufficient heatreleasing function of the heat radiator 107.

As for the interface unit, an interface for wireless communication or aninterface for a coaxial cable may be used.

The invention is not limited to the above-described embodiments, but maybe modified and applied in various forms by a person skilled in the artwithout departing the specification and on the basis of knowntechniques. Therefore, it can be understood that the various forms areincluded in the range of the invention.

What is claimed is:
 1. A communication apparatus which performscommunication through an external power line, the communicationapparatus comprising: a casing with at least two holes; a power plugwhich has at least two connectors corresponding to and passing throughthe two holes, the power plug configured to connect to the externalpower line; a power controller which connects to the power plug andprovides the communication apparatus with a power supply based on powerreceived from the external power line through the power plug; a powerline communicator which transmits a power line communication signalthrough the external power line; and a heat radiator which connects tothe power line communicator and radiates heat generated from the powerline communicator, wherein the power controller is disposed in aparallel direction of the two connectors and extends from the twoconnectors, and all portions of a main body of the heat radiator thatradiate heat, with the exception of a holding frame that structurallyfixes the heat radiator, are not disposed in the parallel direction ofthe two connectors.
 2. The communication apparatus according to claim 1,wherein the heat radiator holds the power line communicator in place. 3.The communication apparatus according to claim 1, wherein the power linecommunicator comprises a first board and a power line communicationcontroller disposed on the first board, managing at least a MAC layerand a PHY layer of the power line communication signal.
 4. Thecommunication apparatus according to claim 3, wherein the powercontroller comprises a second board connecting to the power plug, andwherein the first board overlaps with the second board.
 5. Thecommunication apparatus according to claim 4, wherein a normal line ofthe first board is substantially parallel to a normal line of the secondboard.
 6. The communication apparatus according to claim 4, furthercomprising: a board connector which connects electrically the firstboard to the second board and includes a transmission path for the powerline communication signal, wherein the power line communication signalis transmitted through at least the board connector and the power plug.7. The communication apparatus according to claim 4, further comprising:an interface which receives a digital signal through a transmissionmedium different from the external power line, wherein the interface isdisposed on the second board.
 8. The communication apparatus accordingto claim 4, further comprising: a coupler which is disposed on thesecond board and couples the power line communication signal transmittedfrom the power line communicator to the external power line.
 9. Thecommunication apparatus according to claim 4, wherein the casing isconfigured to accommodate all of the first board and the second board.10. The communication apparatus according to claim 4, wherein the heatradiator is disposed at a location where the heat radiator faces thesecond board.
 11. A communication apparatus which performs communicationthrough an external power line and a transmission medium different fromthe external power line, the communication apparatus comprising: acasing with at least two holes; an electrical plug which has at leasttwo connectors corresponding to and passing through the two holes, theelectrical plug configured to connect to the external power line; apower board which is provided with the electrical plug that is attachedto the power board; a power supplier which generates power based onpower received from the external power line through the electrical plugand supplies the generated power to the communication apparatus; acommunication board which is separately formed from the power board, andis provided with a power line communicator transmitting a power linecommunication signal through the external power line; a board connectorwhich connects electrically the communication board to the power boardand includes a transmission path for the power line communicationsignal; and a heat radiator that connects to the power line communicatorand radiates heat generated from the communication board, wherein thepower board is disposed in a parallel direction of the two connectorsand extends from the two connectors, and all portions of a main body ofthe heat radiator that radiate heat, with the exception of a holdingframe that structurally fixes the heat radiator, are not disposed in theparallel direction of the two connectors.
 12. The communicationapparatus according to claim 1, wherein the heat radiator isplate-shaped.
 13. The communication apparatus according to claim 1,wherein the heat radiator is a metal plate.
 14. The communicationapparatus according to claim 1, further comprising: a plug receiver inwhich the power plug is inserted.
 15. The communication apparatusaccording to claim 14, wherein the plug receiver is disposed at alocation so as not to overlap the heat radiator when viewed from aperspective perpendicular to an external surface on which the power plugis positioned.
 16. The communication apparatus according to claim 1,wherein the casing which accommodates at least the power linecommunicator.
 17. The communication apparatus according to claim 16,wherein the heat radiator is attached to the casing.
 18. Thecommunication apparatus according to claim 17, further comprising: ascrew which attaches the heat radiator to the casing.
 19. Thecommunication apparatus according to claim 16, wherein the casingcomprises a first casing and a second casing.
 20. The communicationapparatus according to claim 16, wherein the power plug is exposed on anoutside of the casing.
 21. The communication apparatus according toclaim 1, further comprising: an interface which performs communicationthrough a transmission medium different from the external power line;and a transmission medium connector which connects the interface to thetransmission medium; wherein the transmission medium connector isexposed on an outside of the casing.
 22. The communication apparatusaccording to claim 21, further comprising: another transmission mediumconnector which connects the interface to the transmission medium and isexposed on an outside of the casing.
 23. The communication apparatusaccording to claim 1, further comprising: a switching power supplierwhich receives power through the power plug and supplies power to thepower line communicator.
 24. The communication apparatus according toclaim 23, further comprising: an AC/DC converter which converts powerreceived through the power plug and supplies the converted power to theswitching power supplier.
 25. The communication apparatus according toclaim 1, further comprising: a first indicator connecting to the powerline communicator; an interface which performs communication through atransmission medium different from the external power line; and a secondindicator connecting to the interface.
 26. A communication apparatuswhich performs communication through an external power line, thecommunication apparatus comprising: a power line communicator whichperforms communication through the external power line; a heat radiatorwhich connects to the power line communicator and radiates heatgenerated from the power line communicator, a casing with at least twoholes which accommodates the power line communicator and the heatradiator; and a power plug which has at least two connectorscorresponding to and passing through the two holes, the power plugconfigured to connect to the external power line and is exposed on anoutside of the casing; a power controller which connects the power plugand provides the communication apparatus with a power supply based onpower received from the external power line through the power plug;wherein the power controller is disposed in a parallel direction of thetwo connectors and extends from the two connectors, and all portions ofa main body of the heat radiator that radiate heat, with the exceptionof a holding frame that structurally fixes the heat radiator, are notdisposed in the parallel direction of the two connectors.
 27. Thecommunication apparatus according to claim 1, wherein all portions ofthe main body of the heat radiator are disposed in a substantiallyperpendicular direction of the two connectors.
 28. The communicationapparatus according to claim 1, wherein there are no other heatradiators connecting to the power line communicator and radiating heatgenerated from the power line communicator.